BI 108- Spring 2007
Major Recalls of Organ Replacement Devices
Saint Gobain Desmarquest Hip Implant
Saint Gobain Desmarquest Hip Implant Recall
Introduction
Zirconium oxide (zirconia) femoral heads were introduced to the market because of their superior strength and wear resistance. When the world’s leading provider of zirconia heads altered a step in their manufacturing process in 1998, the increased fracture rate was not noted until 2000 because of a mean lifetime of 12-32 months before fracturing. Overall, 343 fractures have been reported as a result of the manufacturing change.
Application
Joint failure can be caused by trauma but it most often is the result of aging, combined with obesity. To treat severe joint failure in the hips, hip replacement surgery is called for. The surgery involves removal of bone of the femoral head, femoral neck, some of the Acetabular cup, and all accompanying cartilage. They are replaced with a ball and socket type joint. This study focuses on the femoral head of the device, constituting the “socket”, in the “ball and socket” design.
Most often, ultra-high-molecular-weight-polyethylene is used as the material in the cup because of its reduced friction with femoral heads. However, wear does occur, and results in debris that affect implant life, reduce mobility, and determine the overall success of the implant. In the search for reduced wear characteristics, different heads were used, and it was found that a head made of Zirconia (zirconium oxide ceramic) resulted in less wear of the acetabular cup than its alumina ceramic, and metal counterparts. A study in 1990 by Kumar et al states,
“Depending on the lubricant medium, the wear factor of polyethylene against zirconia ceramic counterfaces was 40 to 60% less than that against alumina ceramic counterfaces, and 5 to 10 times lower than with the SUS316L metal counterfaces.” [1]
Further support came from Good et al in 2003, who found a 61% reduction in polyethylene wear, and 45% fewer polyethylene particles when using roughened OxZr compared with roughened CoCr. [2] In addition to this, Zirconium oxide has the largest fracture resistance of the ceramics at over 10 MPa/m2.
Multiple studies with conflicting reports were later carried out, such as the one from Schewelov et al in 2005. In studying the wear characteristics of zirconia heads on UHWPE, Schewelov fails to reproduce the 60% increase in wear resistance, actually showing a 50% increase in annual wear. [3] Another study in 1999 showed aseptic loosening of the cup. [4] In December 2006, Kraay et al also reported no significant difference in wear rates between zirconia and Co-Cr-Mo femoral heads. [5]
Figure 1: The survival curves for the polyethylene cups when used with zirconia and alumina heads. Taken from Allain, Mouel, et al. [4]
Zirconium Ceramic heads, specifically those marketed by Zimmer were approved to market in 1989 and again in 1995, 1996, and 1997 by the FDA. In its summary, Zimmer cites the success of ceramics over the past 20 years, excellent resistance to corrosion and wear, and biocompatibility. They also state that long term history of yttria stabilized zirconium oxide is unknown, and that with limited clinical and preclinical experience, the biological effects of particulate debris are unknown. The zirconia femoral heads were approved to market by being “substantially equivalent” to a legally marketed predicative device. [6]
Failure Mechanism
Figures 2,3: Evidence of a fracture, Piconi et al. [7], Fractured zirconia head. [8]
Zirconium oxide exists as a crystal whose unit cells contain either cubic sides, a straight prism with rectangular sides, or a deformed prism with parallelepiped sides. Of these forms of crystal, the unit cell in the form of a straight prism and rectangular sides provides the mechanical properties necessary for cohesion of the ceramic particles, such as increased density. The content of the tetragonal phase (straight prism with rectangular sides) directly correlates to fatigue strength, while the monoclinic phase (deformed prism with parallelepiped sides) weakens the mechanical performance of the ceramic. Consequently, manufacturing methods were developed to restrict the formation of the monoclinic phase.
Figure 4: Tetragonal phase (left) and the monoclinic phase (right). The tetragonal phase contributes to the strength of the overall material while the monoclinic phase weakens it. [9]
In order to promote the tetragonal phase, zirconium oxide powder is mixed with yttrium oxide in a specific ratio. Following this, the particles are compressed under 1000 atmospheres of pressure and it is this intense pressure which causes adhesion of the particles. They are then bound together through the process of sintering, which occurs at temperatures ranging from 1400-1500 degrees C. When 1500 C is exceeded, the cubic phase is formed, and below 1400 C results in poor densities. Next, hot isostatic processing is used to improve the density of the zirconia by further heating under high pressures in the presence of inert gases. After this, the zirconia is colored, ground and polished, and machined.
Steam re-sterilization
Zirconia heads in general can fail is if they undergo steam sterilization or re-sterilization. In a statement released by the FDA in May 1997,“…steam sterilization has been associated with surface roughening of zirconia ceramic femoral head components of total hip prostheses. This occurs because exposure to steam and elevated temperatures may lead to a phase transformation in the crystal structure of the zirconia material. As a consequence of this roughening, increased wear on the ultra-high molecular weight polyethylene acetabular component may occur, which can cause premature failure and require early revision.” [10]
It is the monoclinic phase that is formed from the tetragonal phase under autoclave conditions. Manufacturing processes use ethylene oxide, or beta and gamma radiation to sterilize their heads, but the FDA issued a notice to clinicians to avoid steam re-sterilization procedures.
In studying the failure of zirconia heads due to altered thermal processing, Masonis et al also examined monoclinic content of the heads after steam sterilization. Scanning electron microscopy was used to observe changes in the phases of the zirconia heads. For example, in samples where the monoclinic phase was originally absent, the monoclinic content increased to 4.4% after 5 hours of steam sterilization (134 C). [8]
Change in manufacturing procedure
Up until 1997, sintering was performed by SGCA-Desmarquest in a batch furnace, where an array of materials are placed at room temperature, then gradually heated, held at a higher temperature, and finally cooled back to room temperature. In early 1998, the company installed and began using a tunnel furnace, which operates by using a conveyor belt to move the items through multiple heating chambers. As it turned out, the first batches produced were the ones exhibiting the high rates of cracking. In a study of the failure mechanisms, Masonis et al found that the tunnel furnace and batch furnace exhibited the same temperature profiles upon heating to a maximum temperature of 1450 C, but differed in their cooling stage. Masonis found that the time for the materials to reach room temperature was three times shorter for the tunnel furnace than for the batch furnace. Upon examination of explanted, failed heads in the recalled batches, significantly elevated levels of monoclinic phases were found. In fact, a 100% transformation from the tetragonal phase to the monoclinic phase was found near the bore surface in a failed head from the tunnel furnace.
Figure 5: Thermal profile of batch and tunnel furnaces as reported by Masonis et al. [8]
Saint-Gobain Desmarquest reported that using its batch furnace from 1990-1997, of 280,000 heads used, there were only 6 reported fractures equivalent ot about 1 fracture in every 46,000. [11] But once the tunnel furnace was employed, Masonis et al reported a 2.2% overall fracture rate in the 13 batches involved in the recall. This amounts to a 1 in 50 failure rate. Reported failure rates varied from batch to batch. Within the group of 13 recalled batches, the highest failure rate exhibited was 24% or 154 fractures in 655 hips (Batch TH 93038). In America, 39 zirconia heads from this batch were implanted, and by May 2002, 44% had fractured, while another batch, TH 9205 had 68 fractures in 611 patients worldwide.
Figure 6: Shown above are the fragments of the zirconia head removed after revision surgery. [7]
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Recall Statistics
In August 2001, St. Gobain Desmarquest of France recalled nine batches of its zirconia femoral heads (the Prozyr line). St. Gobain Desmarquest manufactures and supplies 80% of the world’s zirconia femoral heads, and thirty-nine companies worldwide employ their zirconia head. At the time of the recall, the FDA estimated that of the 200,000 hip replacement surgeries undergone every year, 6% of those use the zirconia femoral head. The recall was initiated by concern over a higher than expected fracture rate, of 8.8%, in some of the products by St. Gobain Desmarquest. The fractures typically occurred 13-32 months after implantation. As a result, many companies that used the zirconia femoral heads of St. Gobain were affected. Included are:
· Apex Surgical, LLC (Lakeville, Mass.)
· Biomet, Inc. (Warsaw, Ind.)
· DePuy Orthopaedics, Inc. (Warsaw, Ind.)
· Encore Orthopedics, Inc. (Austin, Tex.)
· Osteoimplant Technology Inc. (OTI) (Hunt Valley, Md.)
· Smith & Nephew, Inc. (Memphis, Tenn.)
· Stryker Howmedica Osteonics (Allendale, NJ)
· Zimmer, Inc. (Warsaw, Ind.)St. Gobain reported 162 known failures requiring revision, and that 9,051 heads were involved in the affected batches. Of those 9,051 heads involved, it is unknown how many have already been implanted. [12]
All zirconia heads manufactured by SGCA-Desmarquest after the manufacturing change are under a voluntary recall. In the U.S. the FDA assigned a Class II recall meaning with recommendations that surgeons inform patients who have received the produce of the potential for spontaneous disintegration, resulting in the need for immediate revision surgery. Due to the invasiveness of the procedure, only voluntary revision was suggested. In addition, only zirconium oxide femoral heads since 1998 were recalled, none before the change in manufacturing process. Emphasis should be placed on the fact that not all zirconia ceramic femoral heads made after 1998 will fail, and there are no tests to predict which already implanted heads will fail.
What to do if you have one of these implants
Below are the specific batch numbers of Prozyr Zirconia Head implants involved in the recall. [12]
Batch Numbers
Diameter
Design
TH/ 93038
28
109355/D
190364/B
190572/A
190215/B
TH/ 2957
28
190514
190515
190576/A
190532/A
ou
190533/A
190332/D
190162/F
TH/ 94877
28
195027/A
TH/94878
28
190235/B
TH/ 94879
28
190333/B
TH/ 98260
28
190590&A
TH/ 98282
22
190636
TH/ 3736
28
190515
TH/ 4515
28
190590/A
TH/ 4650
28
190590/A
TH/ 4652
28
190590/A
TH/ 9382
28
190589
Indications that something may be wrong with your artificial hip:
- Sudden difficulty walking
- Sudden pain in your hip
- A jolt in the affected hip
An affected individual should immediately contact their specialist, doctor, or go to the emergency room.
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Patients who already have the implant and do not experience problems are advised against revision surgery. [13]
Resolution
In the end of 2000, distributors of the ceramic head reported a high rate of fractures, especially within one batch. One manufacturer recalled heads from the batch in March 2001, and when multiple failures from other batches were reported in July 2001, SGCA-Desmarquest issued a recall of unused zirconia heads from eight batches. Although the company reported 162 know fractures at the time of the recall, by February a total of 343 fractures were reported. The FDA promptly removed all of St. Gobain’s zirconia femoral heads from the market that were manufactured between 1998 and 2001. [8]
There is sufficient evidence that zirconia femoral heads extend the life of hip implants. However, many feel that because of this recall, surgeons remain concerned about the fracture of implanted ceramic hips. As of late, only 10% of procedures employ a ceramic head.
Generally, the history of zirconia femoral heads has been poorly documented. Multiple studies show conflicting reports of their wear characteristics, and the recall of the Prozyr line of heads by St. Gobain-Desmarquest illustrates the fragility of quality control in ceramics. By changing the type of machine used for sintering, properties of the zirconia crystal were altered (an increase in the monoclinic phase), and a high rate of fractures resulted 12-32 months after implantation. The recall of these zirconia femoral heads serves as a reminder of how important quality control is in the manufacturing of medical devices.
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References
[1] Kumar P, Oka M, Ikeuchi K, Shimizu K, Yamamuro T, Okumura H, Kotoura Y. Low wear rate of UHMWPE against zirconia ceramic (Y-PSZ) in comparison to alumina ceramic and SUS 316L alloy. J Biomed Mater Res. 1991 Jul;25(7):813-28
[2] Good V, Ries M, Barrack R, Widding K, Hunter G, Heuer D. Reduced Wear with Oxidized Zirconium Femoral Heads. J Bone Joint Surg Am. 2003;85:105-110
[3] Schewelov T, Sanzen L, Onsten I, Carlsson A, Besjakov J. Total Hip Replacement with a Zirconium Oxide Femoral Head. J Bone Joint Surg Br. 2005;87-B:12, 1631-1635
[4] Allain J, Mouel S, Goutallier D. Poor eight-year survival of cemented zirconia-polyethylene total hip replacements. J Bone Joint Surg Br. 1999;81(5):835-42
[5] Kraay M, Thomas R, Rimnac C, Fitzgerald S, Goldberg V. Zirconia versus Co-Cr femoral heads in total hip arthroplasty: early assessment of wear. Clin Orthop Relat Res. 2006 Dec;453:86-90
[6] http://www.fda.gov/cdrh/pdf/K971752.pdf
[7] Piconi C, Maccauro G, Pilloni L, Burger W, Muratori F, Richter H.G.On the fracture of a zirconia ball head. J. Mater. Science: Mater. Med. 2006;17:289-300
[8] Masonis J, Bourne R, Ries M, McCalden R, Salehi A, Kelman D. Zirconia femoral head fractures: A clinical and retrieval analysis. The Journal of Arthroplasty, Volume 19, Issue 7, October 2004, Pages 898-905
[9] Dambreville A, Phillipe M, Ray A. Zirconia ceramics or "by night, all cats are grey". http://www.maitrise-orthop.com/corpusmaitri/orthopaedic/mo78_zircone/index.shtml
[10] http://www.fda.gov/cdrh/steamst.html
[11] Clarke IC, Manaka M, et al. Current Status of Zirconia Used in Total Hip Implants. J Bone Joint Surg Am. 2003;85-A Suppl 4:73-84
[12] http://www.rkmc.com/Consumer_Alert_St_Gobain_Prozyr_Zirconia_Ceramic_Coated_Femoral_Head_Hip_Imp
lant_Components.htm[13] http://www.fda.gov/cdrh/recalls/zirconiahip.html
Unassigned references
Maccauro G, Piconi C, Burger W, Pilloni L, et al. Fracture of a Y-TZP ceramic femoral head. J Bone and Joint Surg. November 2004. http://findarticles.com/p/articles/mi_qa3767/is_200411/ai_n9469395
Pulliam I, Trousdale R. Fracture of a Ceramic Femoral Head After a Revision Operation. A Case Report. J Bone and Joint Surg 1997; 79:118-9
http://www.tga.gov.au/docs/html/prostheses.htm
http://www.tga.gov.au/docs/html/qa_prosth.htm
http://www.tga.gov.au/docs/html/hazard.htm
Last Updated: April 30, 2007
